The present invention relates to network processors which transfer network data frames between nodes of a network. Specifically, a process and apparatus for supplying frame type information and information identifying the depth of processing of an ingress processor to an egress processor of a network node is described which avoids redundant frame processing.
Communication network systems transfer information between a source and destination in frames which are transferred between different nodes along the network. The frames contain data destined for the user as well as destination information and other information which is needed for later processing downstream. One of the more common devices for transferring frames of data between nodes is the multi-processor switch. The multiprocessor switch is organized as a series of blades for receiving traffic through multiple ports, and for delivering traffic through other ports on the same or different blades of the switch. The blades typically have an ingress processor associated with them which processes incoming frames by correlating the frame destination with an output port, determining from the frame various parameters which are needed to process the frame, and transferring the processed frame to an egress processor on the same or a different blade. The egress processor may share the same hardware as the ingress processor and run a different set of pico code instructions when it is forwarding frames to an output port of the same blade.
Incoming frames are processed by the ingress processor by parsing the contents of the header, determining a destination for the frame, and then handing off the frame to the appropriate egress processor for processing and forwarding to an appropriate output port. The processing of frames by the ingress and egress processor necessarily requires redundant processing of the frame as it is handed off from the ingress processor to the egress processor. Parsing of header information from the received frame, identifying the frame type as well as other control parameters is part of a frame classification process executed in both the ingress and egress processor. The redundant processing of the frame produces delays in overall device throughput degrading the device performance. The present invention is directed to a system and method which will avoid redundant processing by the egress processor which has previously taken place in the ingress processor.